The present invention generally relates to printer apparatus and methods and more particularly relates to a printer having precision ink drying capability and method of assembling the printer.
An ink jet printer produces images on a recording medium by ejecting ink droplets onto the recording medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the ability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
Ink jet printers comprise a print head that includes a plurality of ink ejection orifices. At every orifice a pressurization actuator is used to produce an ink droplet. In this regard, either one of two types of actuators may be used. These two types of actuators are heat actuators and piezoelectric actuators. With respect to piezoelectric actuators, a piezoelectric material is used. The piezoelectric material possesses piezoelectric properties such that an electric field is produced when a mechanical stress is applied. The converse also holds true, that is, an applied electric field will produce a mechanical stress in the material. Some naturally occurring materials possessing this characteristic are quartz and tourmaline. The most commonly produced piezoelectric ceramics are lead zirconate titanate, lead metaniobate, lead titanate, and barium titanate. When a piezoelectric actuator is used for inkjet printing, an electric pulse is applied to the piezoelectric material causing the piezoelectric material to bend, thereby squeezing an ink droplet from an ink body in contact with the piezoelectric material. The ink droplet thereafter travels toward and lands on the recording medium. One such piezoelectric inkjet printer is disclosed by U.S. Pat. No. 3,946,398 titled xe2x80x9cMethod And Apparatus For Recording With Writing Fluids And Drop Projection Means Thereforxe2x80x9d issued Mar. 23, 1976 in the name of Edmond L. Kyser, et al.
With respect to heat actuators, such as found in thermal ink jet printers, a heater placed at a convenient location heats the ink and a quantity of the ink phase changes into a gaseous steam bubble. The steam bubble raises the internal ink pressure sufficiently for an ink droplet to be expelled towards the recording medium. Thermal inkjet printers are well-known and are discussed, for example, in U.S. Pat. No. 4,500,895 to Buck, et al.; U.S. Pat. No. 4,794,409 to Cowger, et al.; U.S. Pat. No. 4,771,295 to Baker, et al.; U.S. Pat. No. 5,278,584 to Keefe, et al.; and the Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988), the disclosures of which are all hereby incorporated by reference.
The print head itself may be a carriage mounted print head that reciprocates transversely with respect to the recording medium (i.e., across the width of the recording medium) as a controller connected to the print head selectively fires individual ones of the ink ejection chambers, in order to print a swath of information on the recording medium. After printing the swath of information, the printer advances the recording medium the width of the swath and the print head prints another swath of information in the manner mentioned immediately hereinabove. This process is repeated until the desired image is printed on the recording medium. Alternatively, the print head may be a pagewidth print head that is stationary and that has a length sufficient to print across the width of the recording medium. In this case, the recording medium is moved continually and normal to the stationary print head during the printing process.
Inks useable with piezoelectric and thermal ink jet printers, whether those printers have carriage-mounted or page-width print heads, are specially formulated to provide suitable images on the recording medium. Such inks typically include a colorant, such as a pigment or dye, and an aqueous liquid, such as water, and/or a low vapor pressure solvent. More specifically, the ink is a liquid composition comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives and other components. Moreover, the solvent or carrier liquid may be water alone or water mixed with water miscible solvents such as polyhydric alcohols, or organic materials such as polyhydric alcohols. Once applied to the recording medium, the liquid constituent of the ink is removed from the ink and recording medium by evaporation or polymerization in order to fix the colorant to the recording medium. In this regard, the liquid constituent of the ink is removed by natural air drying or by active application of heat. Various liquid ink compositions are disclosed, for example, by U.S. Pat. No. 4,381,946 titled xe2x80x9cInk Composition For Ink-Jet Recordingxe2x80x9d issued May 3, 1983 in the name of Masafumi Uehara, et al.
As previously mentioned, the colorant is heated in order to fix the colorant to the recording medium. Fixing the colorant to the recording medium avoids offsetting of the liquid colorant onto surfaces coming into contact with the printed recording medium. In this regard, there are three distinct methods for heating the colorant. These methods are convection, radiation and conduction. With respect to convection, a heated gas, such as heated air or nitrogen, is blown onto the colorant on the recording medium. However, use of convective heating is thermally inefficient because air and nitrogen have relatively low heat capacities. Thus, relatively high volumes of the air or nitrogen is necessary to transfer sufficient heat to the colorant. Also, relatively large amounts of heat are required in convective heating systems. That is, the air or nitrogen is usually supplied from an external source where the air or nitrogen is stored at a lower temperature. Thus, a significant amount of heat energy must be supplied to the large volumes of the air or nitrogen in order to raise the temperature of the air or nitrogen sufficiently to dry the colorant. Therefore, a problem in the art is the large volumes of gas and large amounts of energy needed in blower-type colorant drying systems.
Radiation heating transfers heat by electromagnetic waves and occurs when two or more spaced-apart objects are at different temperatures. In the prior art, radiation heating of colorants on recording media is typically accomplished by means of infra-red energy applied to the colorant.
Conductive heating typically requires a heating member that contacts the recording medium to fix the colorant to the recording medium. In this regard, the recording medium may be advanced around a hollow drum having hot oil or high-pressure steam in the hollow portion of the drum. The drum can also be heated electrically by radiation or resistive heaters. The drum conducts heat to the recording medium contacting the drum. However, because the drum must sealingly accommodate the hot oil or high-pressure steam, the drum is complex and costly to manufacture. Also, the drum conducts the same amount of heat along the entire width and length of the recording medium regardless of the varying drying requirements of the recording medium. In other words, the same heat is received by areas of the recording medium not having colorant as well as by areas having colorant thereat. Applying heat to areas of the recording medium not having colorant thereat wastes energy. Also, areas of the recording medium that are heavily wetted by the colorant may not receive sufficient heat energy to dry the colorant. Therefore, another problem in the art is applying the same amount of heat to all locations on the recording medium regardless of whether colorant is present at those locations.
An attempt to address the problems recited hereinabove is disclosed by U.S. Pat. No. 6,256,903 titled xe2x80x9cCoating Dryer Systemxe2x80x9d issued Jul. 10, 2001 in the name of Paul D. Rudd. The Rudd device is directed to a drying system in which a substrate is supported about a thermally conductive drum having a plurality of energy emitters disposed circumferentially within the conductive drum at locations along a length of the drum. The plurality of energy emitters are controlled to selectively emit energy along the length of the conductive drum. Moreover, the dryer system preferably includes means for sensing temperatures of the drum along the length of the conductive drum, wherein the energy emitted by the energy emitters along the length of the drum varies based upon the sensed temperatures long the length of the drum. In one preferred embodiment of the Rudd device, the energy emitters comprise annular thin band heaters. Thus, the energy emitters extend along the entire inner circumferential surface of the drum and are positioned side-by-side so as to extend along a substantial portion of the length of the drum. Each annular energy emitter has a diameter comprised for sufficiently encirculating the entire inner diameter of the drum. However, the Rudd patent does not disclose that the energy emitted by the energy emitters varies around the circumference of the drum. Rather, the Rudd patent discloses that the energy emitted by the energy emitters varies merely along the length of the drum. Therefore, the Rudd patent does not appear to disclose control of heat around the circumference of the drum. Thus, in the case of a printed recording medium, a line of printed marks extending the width of the substrate in contact with the drum will receive the same heat input regardless of whether only some locations of the printed line have colorant to be dried. As previously mentioned, applying heat to areas not having colorant thereat wastes energy.
Therefore, what is needed is a printer having precision ink drying capability and method of assembling the printer.
The present invention resides in a printer having precision ink drying capability, comprising a print head adapted to form an ink mark at a location on a recording media; a dryer associated with the print head for drying the ink mark; and a controller coupled to the dryer for controllably operating the dryer, so that the dryer selectively dries only the ink mark.
According to an aspect of the present invention, a printer having precision ink drying capability comprises a print head that is adapted to eject a plurality of ink drops through outlet orifices defined by the print head. The ink drops form a plurality of ink marks at a plurality of locations on a recording medium positioned opposite the outlet orifices in order to define a printed image on the recording media. A plurality of heaters is disposed near the print head and are distributed transversely across the width of the recording media for heating the ink marks on the recording media in order to dry the ink marks. Drying the ink marks fixes the ink to the recording media. A plurality of sensors, disposed near the print head are distributed transversely across the width of the recording media and are coupled to respective ones of the heaters for sensing the locations of the ink marks on the recording media. In addition, a controller interconnects each of the heaters to respective ones of the sensors for selectively energizing the heaters according to the locations of the ink marks sensed on the recording media by the sensors. Thus, the controller selectively informs the heaters of the locations of the ink marks on the recording media as the sensors sense the ink marks. In this manner, the heaters dry only the locations having ink marks. The heaters may be resistance heaters, microwave heaters or radiant heaters. The sensors may be thermocouples or optical sensors.
A feature of the present invention is the provision of a plurality of sensors adapted to sense presence of ink marks comprising the image printed on the recording media.
Another feature of the present invention is the provision of a plurality of heaters coupled to the sensors for heating only the ink marks sensed by the sensors.
An advantage of the present invention is that use of the present invention saves energy.
Another advantage of the present invention is that amount of heat applied to ink marks varies depending on the amount of ink thereat sensed by the sensors.
Still another advantage of the present invention is that speed of printing is increased.
Yet another advantage of the present invention is that scorching of the recording media is avoided.
A further advantage of the present invention is that use thereof avoids use of the large volumes of gas and large amounts of energy needed to heat the gas, as in blower-type ink drying systems.
These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there are shown and described illustrative embodiments of the invention.